As a process for producing BF3 gas, which is a fluoride gas species, known is, for example, a process of causing boron oxide and hydrofluoric acid to react with each other to synthesize an aqueous solution of boron fluoride, and adding at least one of sulfuric acid or fuming sulfuric acid to the aqueous solution, thereby causing a dehydrating effect of sulfuric acid or the like to generate BF3 gas.
Moreover, a process for producing SiF4 is a process (1) of decomposing a metal silicofluoride such as barium silicofluoride thermally, thereby yielding SiF4, a process (2) of causing silicon oxide and fluorosulfuric acid to react with each other, thereby producing SiF4, a process (3) of causing a mixture of silicon oxide and fluorite to react with sulfuric acid, thereby producing SiF4, or some other process.
Furthermore, a process for producing GeF4 may be a process (4) of decomposing a fluorogermanium metal compound, such as barium hexafluorogerumanate thermally, thereby yielding GeF4, or a process (5) of adding, to tetrachlorogermanium, a fluorinating agent, such as zinc fluoride, or a mixture of trifluoroantimony and pentachloroantimony, thereby causing the two compounds to react with each other. Patent document 1 also discloses a process (6) of causing metallic germanium, and fluorine gas or trifluoronitrogen to react with each other, thereby yielding GeF4.
As a process for producing PF5 or AsF5, known are a process (7) of decomposing a fluorophosphorus metal compound, such as lithium hexafluorophosphate, or a fluoroarsenic metal compound, such as lithium hexafluoroarsenate, thermally, and a process (8) of causing a phosphorus pentahalide, or an arsenic pentahalide to react with hydrogen fluoride. Moreover, Patent document 2 discloses a production process (9) of causing a phosphorus trihalide or arsenic trihalide to react with a halogen gas, such as chlorine, bromine or iodine, and hydrogen fluoride.
According to the BF3-producing process, a sulfuric acid waste fluid which contains boron is generated in a large amount; thus, facilities or costs are required in order to process the waste fluid. Additionally, sulfur components such as SO3 are incorporated, as impurities, into the resultant, BF3.
In the SiF4-producing processes (1) and (3), it is necessary to make the temperature of the reaction system high, so that costs required for the heating increase. In the processes (2) and (3), a hydrofluoric-acid-containing sulfuric acid waste fluid and gypsum are generated, respectively, as a byproduct. Costs for processing the byproduct are required.
The GeF4-producing process (4) has a problem that costs required for the heating are high. The process (5) has a problem that a chlorine compound or an antimony compound is incorporated into the resultant, GeF4, so that high-purity GeF4 is not easily obtained, and the process (6) has a problem that GeF4, which is obtained by the reaction, and metallic germanium, which is one of the raw materials, react with each other to generate solid germanium difluoride (GeF2) as a byproduct so that the apparatus or pipe is clogged therewith, whereby a continuous operation thereof may become unable.
The PF5- or AsF5-producing process (7) has a problem that energy consumed for the thermal decomposition is very large. In the process (8), halogenated hydrogen gas, which is a byproduct, is incorporated into the resultant, PF5 or AsF5; and in the process (9), the halogen gas, which is one of the raw materials, as well as halogenated hydrogen, which is a byproduct, is incorporated into PF5 or AsF5. Thus, the processes each have a problem that high-purity PF5 or AsF5 is not easily obtained.